1. Field of the Invention
This invention relates to a vibration dampening assembly. In one of its aspects, the invention relates to a vibration dampening assembly for use in a suspension system in a vehicle. In one of its aspects, the invention relates to a vehicle trailing arm suspension with a vibration dampening assembly. In another of its aspects, the invention relates to a suspension system for use, for example, between a cab and a frame of a truck.
2. Description of the Related Art
In Conaway et al. U.S. Pat. No. 5,253,853, a vibration dampening device is disclosed for use between a truck body and a cab. The vibration dampening device includes a link pivotally mounted at one end to the frame of a truck and pivotally mounted at another end to a lever. The lever is pivotally mounted at one end to a suspended member, for example, a cab of a truck and is pivotally mounted at another end to one end of a shock absorber. The other end of the shock absorber is pivotally mounted also to the suspended body or cab at a pivot point spaced from the pivot point mounting of the lever first end to the suspended body. This device is said to isolate a suspended body or truck cab from the force vibration of the supporting body and provide a non-linear response to vibrational movement of the suspended body with respect to the support body. Whereas some beneficial vibration isolation takes place with a device according to the Conaway et al. ""853 patent, there arc some operational limitations in the design of a suitable dampening assembly and there are practical difficulties in manufacturing this vibration dampening device with proper design characteristics. The distance between the axes of pivot mounts of the lever to the suspended body (main pivot) and the lever to the link controls the relative amount of vertical movement between the suspended and supporting bodies and influences the displacement versus resistive force characteristics of the device. It has been found that the axes of these two pivots should be spaced about xe2x85x9cxe2x80x3 apart. Greater spacing between these two pivot axes gives a wider range of uncontrolled oscillation, and results in a fairly abrupt transition between the oscillation force and dampening force. A smooth transition between the oscillation and the dampening portion of the force versus displacement curve is necessary for an acceptable dampening device. However, at xe2x85x9cxe2x80x3 spacing between the pivot axes, manufacture of the dampening device becomes difficult because the bearings of the pivot axes overlap. However, the geometry of the device precludes this type of arrangement.
Trailing arm suspensions typically have a beam pivotally mounted to a hanger bracket that is mounted to a vehicle frame. An axle is mounted to the beam a spaced distance from the pivot mounting, typically intermediate the ends of the beam. A spring, typically an air spring, is mounted between the frame and the beam, typically at the other end of the beam. The beam can be rigid or flexible. A shock absorber is typically mounted between the axle or the beam and the frame to dampen vibrations between the beam and the frame. These shock absorbers typically have a linear force vs. distance response. An example of a spring beam trailing arm suspension, which is designed for use on a bus steering axle and is identified as AS-090/120/140, has been sold publicly by Holland Neway International, Inc. of Muskegon, Mich., USA since at least 1999.
According to the invention, a vibration dampening assembly for isolating a suspended body from the force vibrations of a supporting body comprises a link member, a shock absorber and a lever member connected between the suspended body and the supporting body. A first plate is adapted for mounting to the suspended body or supporting body. A second plate is adapted for mounting to the other of said suspended body or supporting body. The link member has a first end pivotally interconnected with the second plate at a first support pivot. A lever member is pivotally interconnected with the link member second end at a link pivot intermediate the first and second ends of the lever member. A shock absorber has a first end of pivotally interconnected with the lever member second end at a shock pivot and has a second end pivotally interconnected with the second plate at a second support pivot spaced from said first support pivot. The lever member is pivotally interconnected with said first plate at a main pivot connection located at the first end of the lever member.
In one embodiment of the invention, the first plate is a trailing arm in a trailing arm suspension and the second plate is a portion of a vehicle frame.
In one embodiment, the shock absorber central axis and said lever member longitudinal axis are parallel when the supporting body and suspended body are in a static condition. Preferably, the main pivot connection also lies on the lever member longitudinal axis. Further, the second support pivot also lies on the lever member longitudinal axis. In another preferred embodiment, the link pivot also lies on the lever member longitudinal axis.
Still further according to the invention, a vehicle trailing arm suspension has a variable geometry dampening assembly mounted between a trailing arm and a vehicle frame. The trailing arm suspension comprises a pair of trailing arm assemblies adapted to mount on a vehicle frame having a pair of spaced frame rails. Each of the trailing arm assemblies includes a frame bracket adapted to be mounted to one of the frame rails, a beam pivotally mounted at one end to the frame bracket for pivotal movement about a pivot axis and adapted to carry an axle at another end and a spring mounted to the trailing arm a spaced distance from the one end and adapted to mount to the corresponding vehicle frame rail to resist the rotational movement of the trailing arm toward the frame. The geometry dampening assembly includes
(a) link member having first and second ends, the first end of said link member adapted to be pivotally interconnected with the corresponding vehicle frame rail at a first support pivot;
(b) a lever member having a longitudinal axis and first and second ends, said lever member is pivotally interconnected with the link member second end at a link pivot spaced from the second end of the lever member;
(c) a shock absorber having a central axis and first and second ends, the first end of said shock absorber is pivotally interconnected with the lever member second end at a shock pivot, and the second end of said shock absorber is adapted to be pivotally interconnected with the corresponding vehicle frame rail at a second support pivot spaced from said first support pivot; and
(d) the lever member is pivotally interconnected with said beam at a main pivot connection spaced from said link pivot.
In one embodiment, the link pivot pivotally interconnects the lever member with the link member second end intermediate the first and second ends of the lever member. In this embodiment, the main pivot connection interconnects the lever member with the beam at the first end of the lever member.
In another embodiment, the link pivot pivotally interconnects the lever member with the link member second end at the first end of the lever member. In this embodiment, the main pivot connection interconnects the lever member with the beam intermediate the first and second ends of the lever member.
Other objects, features, and advantages of the invention will be apparent from the ensuing description in conjunction with the accompanying drawings.